<style>
  body {
    background-color: white;
  }
</style>
<svg height="150" width="400">
  <defs>
    <linearGradient id="grad" x1="0" y1="0" x2="70%" y2="0">
      <stop offset="0" stop-color="red" stop-opacity="0.3"/>
      <stop offset="1" stop-color="blue" stop-opacity="0.3"/>
    </linearGradient>
  </defs>
  <rect x="115" y="15" width="170" height="110" stroke="url(#grad)" stroke-width="10" fill="none" />
</svg>
